( Reaffirmed 2001 ) IS :11658 - 1986 Indian Standard GENERAL REQUIREMENTS AND METHODS OF TESTS OF PIEZOELECTRIC CERAMIC PRESSURE TRANSDUCERS DYNAMIC TYPE Piezoelectric Devices for Frequency Control and Selection Sectional Committee, LTDC 12 Representing Physical National New Delhi Laboratory (CSIR ), Chairman Da V. N. BINDAL DR ASHOE KUMAR (Alternate to Dr V. N. Bindal )` Directorate General of Civil Aviation, New Delhi SHRI J. K. BHATTACHARYA SRRI M. P. SAMA ( Alternate ) Electronics Kerela State Development SERI A. SHAEUL HAMEED Corporation Ltd, Cannanore SHRI K. P. N. KUTTY ( Alternate ) Central Electronics Engineering Research DR J. D. JAIN Institute ( CSIR ), Pllani Directorate of Co-ordination ( Police Wireless ), SERI S. JANAEIRAMAN New Delhi SRRI R. P. MATHUR SERI M. R. NATRAJ Indian Telephone Industries, Bangalore SHRI H. S. ANANT~ANARYANA RAO ( Alternate ) Bharat Electronics Ltd, Bangalore SHRI M. PRABHAEARAN SHRI R. SRINIVASA RAO ( Alternate ) All India Radio, New Delhi SHRI W. V. B. RAMALINQAM SHRIMATI SUDHA BEATIA ( Alternate ) Central Glass & Ceramic Rrscarch Institute DE P. SAHA ( CSIR ), Calcutta SHRI ANNAMALAI ( Alternate ) Ministry of Defence ( R & D ), Bangalore SHRI H. B. V. SHANBHOWJE ( Cotrfinzled on pngc 2 ) ( Alternate ) INDIAN Q Copyright 1987 STANDARDS INSTITUTION This publication is protected under the Indian Cofyrighf Act ( XIV of 1957 ) and reproduction in whole or in part by any means except with written permission of the publisher shall be deemed to be an infringement of copyright under the said Act. IS:11658-1986 (Contintrcdffom page Members SHRI NARENDRA SHARMA 1) Representing Department Delhi Director of Telecommunication IS1 (Ex-o&o Board, New SHRI J. S. BAWA (Alternate ) SHRI N. SRINIVASAN, Director ( Electronics ) General, Member) Sscretnry SHRI B. K. SHAIWA Deputy Director (Electronics), IS1 Panel for Piezoelectric Ceramic Materials LTDC 12 : PI National Physical New Delhi and Its Devices, DR V. N. BINDAL Laboratory (CSIR;, Members &RI G. S. DHAMI DR J. D. JAIX SRRI S. V. PINGALA Armament Research & Development Establishment ( Ministry of Defence), Pune (Alternate) Central Electronics Engineering Research Institute I CSIR 1. Pilani National Physical ' ' Laboratory ( CSIR ), New Delhi Concord Electroceramic Industries, Delhi Bharat Electronics Ltd, Bangalore Natiro;lThysical Oceanography Laboratory, Central Electronics Ltd, Sahibabad DRJ~NARDHAN SINGE SHRI A. KASHYAP DE J. L. MUXHERJEE SHRI A. S. RA~.~AWOORTHY DR B. V. RAO 2 IS: 11658-1986 Indian Standard GENERAL REQUIREMENTS AND METHODS OF TESTS OF PIEZOELECTRIC CERAMIC PRESSURE TRANSDUCERS DYNAMIC TYPE 0. 0.1 This FOREWORD Indian Standard was adopted by the Indian Standards Institution on 31 January 1986, after the draft finalized by the Piezoelectric Devices for Frequency Control and Selection Sectional Committee had been approved by the Electronics and Telecommunication Division Council. 0.2 For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS : 2-1960". The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard. 1. SCOPE 1.1This standard deals with the general requirements and tests of piezoelectric ceramic pressure transducers - dynamic 2. TERMINOLOGY 2.1 In addition following terms to the definitions given in and definitions shall apply. IS : 1885 (Part 44)-197&t methods type. of 2.1.1 Measuring Range - The pressure values within which a transducer is intended to measure, specified by their lower and upper limits. 2.1.2 Resolution - The smallest change ( increase or decrease ) in mechanical input at any intermediate point in the measuring range which produces a detectable change in the output signal. *Rules for rounding off numerical values ( r&cd). tElectrotechnica1 vocabulary: Part 44 Piezoelectric devices. 3 Is: limit 11658-1986 of measuring range smallest increase in pressure that can be detected. Change in output charge p ( kPa), that is, dQ/dp. voltage Q above the lower 2.1.3 &`cnsitivity - The 2.1.4 Charge Constant due to change in pressure 2.1.5 change ( pica coulomb ) I' ( volts ) due to Voltage Constant - Change in output in pressure p ( bar ), that is, dV, dp. 2.1.6 Linearity - It is defined as the closeness of the calibration curve from a straight line drawn between lower and upper limits of measuring It is expressed in percentage of the upper limit of measuring range. range. 2.1.7 Reproducibility -The ability of the pressure transducer to reproduce output reading when the same pressure is applied to it repeatedly under the same conditions and in the same direction. 2.1.8 Hysteresis - The maximum difference between the output reading of the transducers for the given input ( usually at the half value of the specified range ) when the value is approached first with increasing and then with the decreasing input pressure. hysteresis, reproducibility 2.1.9 Accurac3; - The total of linearity, any other term such as resolution, expressed in percentage. 2.1.10 Resonant Frequency at which of transducers, amplitude. It is the first mechanical it responds with the and resonant frequency maximum output 2.1.11 Cupacitance - The capacitance measured between the two terminals. value of pressure transducer 2.1.12 Insulation Resistance -- The resistance measured between specified insulated portion of a transducer and the two terminals jointed together with a shunt when a specified dc voltage is applied at room conditions, unless otherwise stated. 2.1.13 Maximum Safe Pressure --It transducer without causing any characteristics. 2.1.14 area. 2.1.15 produces Pressure -Force acting is shift the pressure applicable on beyond specified performance on a surface measured as force per unit Pressure Transducer - A device an electrical signal proportional 4 which senses to the pressure. pressure and IS : 11658- 1986 2.1.16 Gauge Pressure referenced to local Transducer - A device that atmospheric pressure and is vented measures pressure to atmosphere. the device will NOTE -When its pressure port is exposed to the atmosphere, indicate 0 pressure. 2.1.17 Sealed referenced pressure. to Pressure Transducer an internal chamber A device typically that measures pressure sealed at atmospheric pressure may be required NOTE -Corrections when making gauge pressure measurements due to changes in atmospheric below 700 kPa. 2.1.18 Absolute Pressure Transducer referenced to an internal chamber A device that measures sealed at 0 pressure. the atmosphere, pressure its pressure port is exposed to NOTE -When will indicate atmospheric pressure. the transducer 2.1.19 Di#erenciaE difference between Pressure Transducer - A device that measures two pressures applied to its pressure ports. the transducers may be classified as either unidirectional or NOTE -These bidirectional depending on whether or not the higher of the two pressures is always applied to the same pressure port. 2.1.20 Combined Error-The total of all deviations of a transducer output from a specified straight line in a constant environment defined as the sum of the errors due to non-linearity, reproducibility and hysteresis. 2.1.21 Full Scale Output -The algebraic difference values measured at zero and full scale pressures. of transducer output under 2.1.22 zero Balance ( Offset ) - The measured transducer output room conditions with no pressure applied to the pressure port. NOTE - For absolute pressure transducers, this value is measured at 0 pressure. Gauge and sealed pressure transducers have this value measured at atmospheric pressure. 3. WORKMANSHIP, PROCESSES AND FINISHES shall be manufactured and piezoelectric pressure transducer processed in careful and workmans' like manner in accordance with good engineering practices. The metal parts shall be free from burrs, sharp edges and corrosion effects. 3.1 The 4. CLASSIFICATION 4.1 The piezoelectric pressure measuring O-1 000 MPa may transducers - dynamic type, capable of be classified in the following categories 5 IS I 11658 - 1986 depending upon the measuring Category Category Category Category 5. REQUIREMENTS 1 2 3 4 ra.nge: O-1 O-10 O-100 MPa MPa MPa O-1 000 MPa 5.1 Maximum Safe Pressure - The maximum safe nressure shall be at least three times the upper limit of the measuring range in case of categories I, 2 and 3 and at least two times for category 4. following parameters may be 5.2 Performance Requirement - The specified for the performance requirement. 5.2.1 Resolution is as follows: The recommended Category Category Category Category 5.2.2 Linearity categories. 5.2.3 Hysteresis all categories. -Shall -Shall be 1 2 3 4 within order of resolution 0.01 0.1 1 10 kPa kPa kPa kPa for for each range 2 percent transducers of all of for to not be more than 3 percent Shall not be less for transducers 101? ohms -40°C 5.2.4 Insulation Resistance transducers of all categories. 5.2.5 + 85°C than Working Temperature Range - Shall for transducers of all categories. be at least between not be more than 50 percent of 5.2.6 Working Frequency -Shall resonant frequency ( fr ) or shall be at least 5 kHz less than the resonant frequency ( fr-5 kHz ) , whichever is lower. 6. METHODS OF EVALUATING THE QUALITY PIEZOELECTRIC TRANSDUCERS - DYNAMIC OF TYPE 6.1 General pressure - The methods of evaluating the characteristics of dynamic transducers are similar to those employed for the evaluation of 6 IS : 11658 - 1986 static pressure transducers based on potentiometric and strain gauge principles, except that the input amplifier/impedance converter should always be used as a part of the transducer during the tests. The impedance converter should have a flat frequency response from DC to 250 kHz. A high speed readout system such as a storage oscilloscope or a peak meter indicator is employed for recording transducer output signal. The pressure source employed may be either pneumatic or hydraulic with provision to generate sinusoidal output, pulsed output, step output and ramp output. The characteristics could be assessed in comparison with a secondary standard transducer wherever feasible. 6.2 Instrumentation - The basic instrumentation set up required for It calibration of a pressure transducer is shown schematically in Fig. 1 consists of a standard pressure source, charge amplifier, additional voltage amplifier ( if necessary) and a suitable read-out device. Sl4m4RD PRESSURE SOURCE RE4Dd Ou7 DEW -D PRESSURE TR4NlUER -) CHARGE 4MPLIFIER -+ voLT46E 4LyPLIFIER FIG. 1 BASIC CALIBRATIONSYSTEMFOR PRESSURE TRANSDUCER 6.2.1 Charge Ampl$eer - The charge amplifier should have very high input impedance of the order of lOI3 ohms for piezoelectric ceramic transducers. The frequency response of the combined system ( transducer i_ Amplifier + read-out devices) for any measurement should be flat over a certain specified frequency range. 6.2.2 Voltage Amplifier and Read-Out Device - The additional amplifier stages are essential for the effective and proper recording of weak signal encountered in measurements. A high speed read-out system such as storage oscilloscope or peak level indicator is employed for recording output signal. 6.2.3 Pressure Source - In the calibration procedure, a known and accurate dynamic pressure is applied to the pressure transducer using standard pressure sources and a corresponding electric charge developed on the transducer is measured by a suitable charge amplifier and readout system as shown in Fig. 1. The three pressure sources, namely, shock tube, dead weight tester and hydraulic pressure vessel generate pressure pulses of different durations of the order of 1 microsecond, 0.5 milli-second and around 5 milli-seconds, respectively. Hence a proper pressure source can be selected for the calibration of a particular type of transducer. The details of these sources are given in subsequent clauses. IS : 11658- 1986 6.2.3.1 Shock tube - The shock tube is a basic device for the generation and propagation of shock waves. The media used for the generation of shock wave is usually atmospheric air and in some cases nitrogen and other gaseous substances are used. The shock tube produces one dimensional shock wave which travels down the tube with a velocity The shock several times the speed of sound within a few microseconds. wave is generated by bursting a diaphragm placed in between a pressure chamber and the tube ( see Fig. 2 ). For shock pressure computation and oscilloscope triggering, two integrating circuit piezoelectric transducers are installed on the walls of the tube. A third transducer, under dynamic response and calibration test, is mounted in the closed end of the tube with. its sensing diaphragm flush with the inner wall. The step pressure function can be readily generated in the shock tube for the calibration of pressure transducers dynamically. The shock tube generates a pressure pulse of the order of 10 kPa and duration around one microsecond. The calibrations/sensitivity at lower pressure levels holds good at high pressures also. FIG. 2 SHOCK TUBE 6.2.3.2 Dead weight tester - It is a most common pressure calibrating source using mineral oil as a pressure transmitting medium. It essentially consists of a piston of very accurately measured cross-sectional area which is closely fitted within a cylinder. Known weights are placed on piston and the load acting on the piston is converted into a pressure which is in turn applied to the liquid by compressing it within the liquid. The schematic diagram is shown in Fig. 3 which is self explanatory. The oil is filled in the cylinder by the priming pump When the value is opened the pressure is raised with the help of the hand operated screw unit1 it balances to pressure exerted by the weighted piston so that the piston floats freely in the oil. In this situation, piston floating freely in the oil, the pressure is applied to the oil and in turn it is transmitted to the transducer. 8 IS:11658 - 1986 CHARGE OlJlpuJ TD PREAWLIFIER PISTON II II II t--PRIMING m TRANSWCER FIG. 3 DEAD WEIGHT TESTER PRESSURE CALIBRATION The transient pressure pulse is obtained by releasing the pressure suddenly by a mechanical device. The applied to the transducer duration of the pressure pulse can be varied by changing the dead weight load on the piston. 6.2.3.3 Dynamic hydraulic test Pressure vessel - The schematic of the system is given in Fig. 4 which is quite self explanatory. diagram By changing the dropping weight the amplitude of maximum pressure can be readily varied. The duration of the pressure pulses can be readily varied by using oils of different viscosities. The dynamic pressure pulses of 0.5 to 2 ms durations up to 6 000 kPa can be very conveniently generated by this method. A comparative characteristic of the pressure transducer can be obtained by this test vessel. The pressure pulses of higher amplitudes can be achieved with suitable modifications in the design of the system. 6.3 Methods of Evaluation 6.3.1 Category --- The category of piezoelectric pressure transducer is evaluated, over the specified range, by comparing its signal output with that of a secondary standard transducer which has already been calibrated. 9 IS : 11658- 1986 Increase the pressure applied to the transducer from zero to full-scale level, in 10 definite steps, and record the signal output in each case with a peak level meter or a calibrated storage oscilloscope. Plot the reading; on a graph showing the transducer output versus applied pressure ( Fig. 5 ). Repeat the experiment three times. STAND WEIGHT FIG. 4 SCHEMATIC OF DYNAMIC TEST VESSEL F.gJ _--_- _____ -- 5 0 2 3 s e * s / FS PRESSURE FIG. 5 10 RANGE IS : 11658- 1986 within range. The range over which the performance of the transducer is well specifications ( given by the manufacturer ) shall be its measuring 6.3.2 Maximum Safe Pressure - After the test specified in 6.3.1, apply a pressure of magnitude two or three times more as specified in Fig. 5 and hold it constant for two minutes. 6.3.3 Resolution - Apply a pressure equal to 50 percent of the full-scale range of the device and record the output as before. Increase the pressure now in small steps, say of 0.5 percent of FS, and observe the increments in the output for at least 3 steps, with a high resolution digital voltmeter. Repeat the experiment by decreasing the pressure level in steps of 0.5 percent FS from the original value and record the readings as before. Draw a curve ( Fig. 6 ) showing the variations in output for corresponding changes in pressure input and from this evaluate the resolution of the transducer, as defined in 2.1.2. __--- -------`1 CHANGE IN PRESSURk IAPI FIG. 6 RESOLUTION Repeat the experiment and 70 percent of FS. at two other points over the range, say at 3 6.3.4 LinearityRepeat the experiment 6.3.1 and draw a curve ( Fig. 7 ) showing the transducer output over the measuring range. Evaluate the linearity of the transducer as defined in 2.1.6. 6.3.5 Hysteresis -Repeat the experiment 6.3.1 and draw a curve ( Fig. 8 ) showing the transducer output over one complete cycle when taken from zero to full-scale and from full-scale back to zero. Evaluate the difference in output at 50 percent of the range and compute the hysteresis factor as defined in 2.1.8. 11 IS : 11658- 1986 Fs PRESSURE FIG. 7 LINEARITY PRESSURE~PERCEN~ FSl FIG. 8 HYSTERESIS set up for rise time is as shown in 6.3.6 Rise Time - The measurement Fig. 2. Puncture the diaphragm either electrically or mechanically so that a pressure pulse is generated in chamber No. 2 where the transducer under evaluation is installed. Record the transducer output on a calibrated cathode ray oscilloscope and evaluate the rise time of the transducer in accordance with the curve given in Fig. 9. the insulation resistance between 6.3.7 Insulation Resistance - Measure the terminals or leads and the metal housing of the transducer with a standard megohm meter, applying a dc potential of 50 volts. (For this measurement the potential shall be retained for a period of two minutes, unless otherwise specified ). 12 s 5 z % ,I z ?I . _ /r,M) ____-------90_---___ IO,-- : I E, E2 TIME c FIG. 9 RISETIME the working temperature 6.3.8 Working Temperature Range - Evaluate range of the transducer by either of the following two methods: a) Calibrate the transducer 6.3.4 ) at discrete ambient + 150°C ( unless otherwise (repeating experiments 6.3.1 and temperatures ranging from - 50°C to specified ) in steps of 10°C. b) Soak the transducer for one hour at the lowest temperature (as specified ) and conduct the calibration tests at standard reference temperature ( 27°C ). Next, soak the transducer for one hour at the highest temperature ( as specified ) and conduct the calibration tests at the standard reference temperature. The range over which the performance of the transducer is within the given specifications shall be the working temperature range. 6.3.9 Working `Frequency- The working frequency of a piezoelectric pressure transducer is established either with a shock tube or with a For larger range transducers the shock sinusoidal pressure generator. tube method is preferred. Apply a pressure in step of definite magnitude to the transducer and record the electrical signal output on a cathode ray oscilloscope. Evaluate the frequency response from the type curve obtained. The sinusoidal pressure signal system is employed, if the range of the transducer is rather low and the frequency of interest ir limited up to 20 Hz. 7. MARKING 7.1 Each piezoelectric following information a) Type pressure transducers, legibly and indelibly transducers, 13 dynamic type, shall have the marked upon it: of pressure 16:11658-1986 b) Measuring c) Working range, and frequency. dynamic type, may also be 7.2 The piezoeIectric pressure transducers, marked with the IS1 Certification Mark. Mark is governed by the provisions of NOTE - The use of the IS1 Ccrtifica&m the Indian Standards Institution ( Certification Marka) Act and the Rules and Regulations made thereunder. The IS1 Mark on products covered by an Indien Standard conveys the assurance that they have been produced to comply with the requiremehts of that standard under a well-defined rysrem of inspection, testing and quality control which is devised and supervised by IS1 and operated by the producer. ISI marked products are also continuously checked by IS1 for conformity to that Details of conditions under which a licence for the standard as a further safeguard. use of the IS1 Certification Mark may be granted to manufacturers or processors, may be obtained from the Indian Standards Institution. . 1( Is ._ 14